Merge pull request #622 from mgsergio/time_t-to-w3c-datetime

W3C time functions.

base/base.pro

@@ -31,6 +31,7 @@ SOURCES += \
     thread_pool.cpp \
     threaded_container.cpp \
     timer.cpp \
+    w3ctime.cpp \
 
 HEADERS += \
     SRC_FIRST.hpp \
@@ -81,4 +82,5 @@ HEADERS += \
     threaded_list.hpp \
     threaded_priority_queue.hpp \
     timer.hpp \
+    w3ctime.hpp \
     worker_thread.hpp \

base/base_tests/base_tests.pro

@@ -39,5 +39,6 @@ SOURCES += \
   threads_test.cpp \
   timer_test.cpp \
   worker_thread_test.cpp \
+  w3ctime_test.cpp \
 
 HEADERS +=

base/base_tests/w3ctime_test.cpp

@@ -0,0 +1,19 @@
+#include "testing/testing.hpp"
+
+#include "base/w3ctime.hpp"
+
+using namespace base;
+
+UNIT_TEST(ParseTime)
+{
+  TEST(NotATime(ParseTime("")), ());
+  TEST(NotATime(ParseTime("2015-10-11 23:21")), ());
+  TEST(!NotATime(ParseTime("2015-10-11T23:21Z")), ());
+  TEST_EQUAL(ParseTime("2015-10-11T23:21Z"), 1444605660, ());
+}
+
+UNIT_TEST(TimeToString)
+{
+  TEST_EQUAL(TimeToString(0), "1970-01-01T00:00Z", ());
+  TEST_EQUAL(TimeToString(1444605660), "2015-10-11T23:21Z", ());
+}

base/w3ctime.cpp

@@ -0,0 +1,43 @@
+#include "w3ctime.hpp"
+
+#include "std/array.hpp"
+
+// It would be better to use c++ standard means of
+// time parsing and unparsing like
+// time_get/time_put (<locale>) or get_time/put_time (<iomanip>).
+// But at the moment of writing they was not widely supporded
+// and/or worked incorrect.
+//
+// All covertions are made in UTC
+
+namespace
+{
+char constexpr kW3CTimeFormat[] = "%Y-%m-%dT%H:%MZ";
+
+// Two more digits for year.
+size_t constexpr kBufSize = sizeof(kW3CTimeFormat) + 2;
+} // namespace
+
+namespace base
+{
+time_t ParseTime(std::string const & w3ctime) noexcept
+{
+  std::tm tm{};
+  if (strptime(w3ctime.data(), kW3CTimeFormat, &tm) == nullptr)
+    return -1;
+
+  return timegm(&tm);
+}
+
+std::string TimeToString(time_t const timestamp)
+{
+  std::tm tm{};
+  array<char, kBufSize> buff{};
+
+  gmtime_r(&timestamp, &tm);
+  if (strftime(buff.data(), kBufSize, kW3CTimeFormat, &tm) == 0)
+    buff[0] = 0;
+
+  return buff.data();
+}
+} // namespace base

base/w3ctime.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "std/ctime.hpp"
+#include "std/string.hpp"
+
+namespace base
+{
+
+inline bool NotATime(time_t const t) noexcept { return t == -1; }
+
+// See http://www.w3.org/TR/NOTE-datetime to learn more
+// about the format.
+
+// Parses a string of a format YYYY-MM-DDThh:mmTZD
+// (eg 1997-07-16T19:20:30.45+01:00).
+// Returns timestamp corresponding to w3ctime or -1 on failure.
+time_t ParseTime(std::string const & w3ctime) noexcept;
+
+// Converts timestamp to a string of a fromat YYYY-MM-DDThh:mmTZD
+// or empty string if cannot convert.
+std::string TimeToString(time_t const timestamp);
+} // namespace base